Existing liquid crystal displays (LCDs) modulate light by placing liquid crystals (LCs) between two optical polarizers of crossed (e.g., rotated 90 degrees relative to each other) polarization. Consider a photon moving through Cartesian space towards a pair of crossed optical polarizers. If the photon is polarized along the x-axis and is propagating along the z-axis, it will pass through the first optical polarizer if the polarizer is aligned along the x-axis. When this photon arrives at the second, crossed polarizer which is aligned along the y-axis, the photon will be absorbed or reflected, depending on the type of polarizer. In principle, no light will get through the crossed polarizers. However, the orientation of the LC material disposed between the polarizers can rotate the polarization of the photons to allow light through the stack. The amount of rotation is determined by an electric field which is controlled by thin-film transistors (TFTs) fabricated within the LCD.
Conventional optical polarizers are absorptive. For example, more than 50% of the unpolarized light produced by the backlight of the LCD is absorbed by the first polarizer alone. Such arrangements essentially consume light, converting the energy into heat within the first polarizer and are therefore inefficient.
Optical filters (other than polarizers) are used to adjust performance characteristics of displays such as the degree of neutrality and level of transmitted color, the level of reflected radiation, and the transmission levels of undesirable near infrared and electromagnetic interference (EMI) radiation. Such filters with EMI shielding have been developed that can modify visible radiation, infrared radiation, adjust color, reduce reflection, and can provide EMI radiation shielding between various electronic components within device (including the display) from each other. Typically, a number of different optical filter films along with a separate EMI shielding film (e.g., a film with a transparent conductive mesh configuration) have been used to produce the final, desired visual output of the device. Some of these optical filters have employed interference stacks (e.g., Fabry-Perot) of alternating conductors and dielectrics to adjust the optical performance characteristics of the filters, while also providing EMI shielding. The conductors in these stacks are usually separate metal layers and the dielectrics are usually metal oxides layers. The metal oxide layers can have a very slow deposition rate which can lead to high production costs. The use of multiple optical filters in electronic devices to obtain desired performance characteristics can increase costs, make the devices bulky, and cause considerable loss in transmission of the desired images.
Therefore, what is needed are improved systems, apparatus, and methods for both providing optical polarization efficiently and EMI shielding without increasing the expense and bulk of displays.